Time-limit device for electric switches.



G. A. BURNHAM.

TIME LIMIT DEVICE FOR ELECTRIC SWITCHES.

APPLICATION FILED H18. 3, 1910.

979,256, Patented DGQZO, 1910.

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ll/Zinesses:

G. A. BURNHAM.

TIME LIMIT DEVICE FOR ELECTRIC SWITCHES.

APPLIGATION FILED FEB. 3, 1910.

Patented Dec. 20, 1910.

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, UNITED STATES PATENT OFFICE GEORGE A. BURNHAM, OF SAUGUS, MASSACHUSETTS, ASSIGlIOR TO S. B. CONDIT, JR.,

OF BOSTON, IASSACHUSETTS. I

TIM -Linn DEVICE ron ELECTRICQSWITCHES.

Specification of Letters Patent.

Patented Dec. 20, 1910.

Application filed February 3, 1910. Serial No. 541,721.

To all whom it may concern:

Be it known that I, GEORGE A. BURNHAM, of Saugus, county of Essex, and State of Massachusetts, have invented an Improvement in Time- Limit Devices for Electric Switches, of which the following a specification.

This invention relates. to time-limit devices for electric-switches, and has for its object to provide the controlling-device for the electric-switch with means adapted to be operated at a variable speed, whereby the time consumed in operating it may be varied automatically; also to provide a timed operating-device for the controlling-device for the electric-switch, with means, such, for instance, as an electric-motor having the gencral characteristics of a series type of motor, for operating it at a variable speed, according to the strength of the current passing through it; also, to improve the construction of the timed operating-device whereby its normally disengaged parts may be brought into engagement by mechanical means; also, to provide for operating the mechanical means employed for moving the parts of the timed operating-device into engagement by means employed for subsequently operating the timed operating-device, whereby a single actuator may be employed for accomplishing these results; also,

to provide means for re-setting the partswhen the motor or other actuator ceases to operate; also, to provide the circuit with an overload-relay having means for normally shunting the'time-limit device, and also a switch adapted to control the circuit of the controlling-device electric-switch, whereby said circuit may be controlled by both the time-limit device and the overloadrelay, in the former instance the circuit being operated by a slight overload after a prolonged, period of time, and in the latter instance by a heavy overload instantly.

Figure 1 is a side elevationof a time-limit device for electric-switches embodying this invention, the parts being in their normal positions ofv rest. Fig. 2 is a detail of a portion of the device shown in Fi 1, the parts being in the positions they wi occupy when in operation. Fig. 3 is a side elevation of an overload relay adapted to be employed in connection with the time-limit device. Fig. 4 is a diagram illustrating the invention as applied to a polyphase system of electrical distribution. Fi 5 is a similar diagram illustrating the invention as applied to a single-phase system of electrical distributlon.

, Referring to Fig. 4, wherein a three-phase system is illustrated, a, b, 0, representing the three phases of the circuit, two currenttransformers, d and d, are respectively represented as installed in circuit-wires a and c, and overload-relays d (i are arranged in the transformer circuit, with one end of each coil connected respectively to the currenttransformers by circuit-wires 2,. and the other ends thereof connected together by circuit-wire 3. The'armatures or cores of the relays have connected with them, by rods d or otherwise, suitable contact-plates d, which normally rest on contacts d, d, which are connected by circuit-wires 4:, re-

spectively with circuit-wires 5 leading to the current-transformers, and are connected together by a circuit-wire 6. The circuit-wire 6 is also connected with a circuit-wire 3 by a circuit-wire 7 With this arrangement the current normally passes through the contact plates at", d, and contacts on which they rest.

As an actuator for thetime-limit device I prefer to employ an electric-motor, e, of the series type, or one having the general characteristics of a series type of motor, whereb the speed of its armature is variable accor ing to the strength of the current, but, so far as some features of my invention are concerned, any other type of electric-motor or any other kind of motor may be employed. Ashore shown said motor is connected by circuit-wires 8 and 9 leading to the circuit-wires 5, 5, and hence is arranged naled at the extremity of the arm a of a bell-crank lever, which is pivoted at e to a suitable support, the other am e of said lever having a bifurcated end 'ada ting it to engage a pin a extended from a eeve e arranged on a sliding-collars, arranged on the motor-shaft near the threaded portion thereof. As said bell-crank lever is moved on its pivot, said worm-wheel is moved into and out of engagement with the worm e. To move the bell-crank lever, and thus control the engagement of the worm wheel and worm, the collar 0 is moved along on the shaft, and, to accomplish this result, a device, acting by centrifugal force, or other means operated mechanioall by the shaft, is employed. Said mechani 'device, as here shown, consists of a collar 7, pinned or otherwise secured to the shaft, bearing a pair of ears f, f, to which are loosely or pivotally connected a pair of-links f, f, which are loosely orpivotally connected to arms f f which are loosely or pivotal-1y connected at one end to ears on the'slidin collar 6, and hear at their extremities -b s f, f. Said sliding-collar is movable horizontally on the shaft and may be kept in erate the controlling-device for t position by a spline, and aspring f is arranged on the shaft between the fixed and movable collars, acting to force the movable collar away from the fixed collar, but yielding when the shaft is rotated, and the ball-carrying arms are swung outwardly by centrifugal action. When the shaft is at rest, the ball-carrying arms resume .a position closeto the shaft, and the bell-crank lever is moved to disengage the wormwheel from the worm, but when the shaft is rotated and the sliding-collar'is moved along on the shaft mechanically by the outwardly moving ball-carryin arms, due to centri ugal action, said be l-crank lever is moved to cause the worm-wheel to engage the worm, and said engagement will continue while the shaft continues :to revolve. For said mechanical-device to move the wormwheel into engagement with the worm requires an appreciable length of time, and such time will vary according to speed of shaft of the motor. The worm-wheel has connected with it a spring 6 adapted to return it to normal pos tion when disengaged from the worm, said return movement being limited by the pin a tfixed to a suitable support, which is enga d by a stop-pin e on the worm-whee Said worm-wheel -is provided with a series of holes, e although one only may be -employed if desired, and :said holes are arranged circulazcly-about its a and a large pin e is adapted to be plea in any one of the holes. Said pin' c, moved-by the worm-wheel is employed to'engage and opswitch, which is here shown as a pair of arm, so that sai 7 e" I enga e electric-' circuit-contacts e, e, arranged to control a circuit (2 containing a trip-coil t, by which one or more switches may be operated to 0 en the main circuits. One or both of said circuit-contacts is flexible, and they are arranged on suitable supports and adapted to be moved, one into and out of engagement with the other, to close and open the circuit 0 the movable contactmember 6" being arranged in the path of movement of said pin e", 50 as to be engaged by said pin as the worm-wheel revolves. It will be observed that adjustment as to time maybe made by placing the pin in the different holes. In lieu of the particular form of controlling-device for the electric-switch here shown-other forms may be employed.

Referring again to the overload relays, both of which are or may be made alike, see

Fig. 8, the armature or core d has secured to it .-a non-magnetic rod (1", vertically adjusted bya nut (1 The contact-plate d is pivotally connected to said rod (1 so as to engage the pair-of contacts (2", d. Said rod extends through a hole in a pivoted arm d", and has arranged on its lower screw-threaded end a nut d, which en ages the under side ofsaid arm will be lifted by an upward movement of the core of the relay. Said pivoted-arm bears a contact-plate d, which is adapted to engage a contact-plate d, when the arm is raised by an upward movement of the core of the relay, and to disengage said contact-plate when said arm is returned by a spring d attached toit. Said contact-members d and d also control the circuit of the tri .-coil t.

The operation .is as ollows: Suppose a current should flow slightly in excess of that required to lift the core of the overload-relay to-disengage the contact-members d, d", and slightly extend the spring cl but not sufii-. cient to extend said sprmg far enough to cause the contact-members d, l ,to enga e,

then it -will be seen that the shunt-circuit or 'worm-wheel will be revolved until the pin -e" engages the contact-member and closes the. circuit of the trip-coil to operate the switch, but if the excess of current should .-not be prolonged sufliciently to accomplish this wresult, and should cease before the pin s the contact-members", then said worm-w eel will be automaticallyrestored tonormal .position, and the parts will resume theirinormal positions automatically. Should the excessivecurrent be what is ordinarily called -.a short-circuit, the spring-"11" of the overload-relay will be quickly extended, and the contact-member al moved into engagement with the contact-member ti, and, as these contacts are arranged in multiple with the contact-members, the trip-coil t will be operated and the switch opened.

The employment of a series-motor, or motor having the characteristics of a seriesmotor, is of material advantage for the reason that -the load is practically constant, and, by keeping the flux density of the magnetic circuit extremely low, the speed of rotation of the motor-shaft will increase with the increasing current through the coils of the motor-armature that is to say, if the time-limit device is set, so that the switch will be opened in two seconds on a current of five amperes, a lesser period of time would be required to accomplish the same result on a current of ten amperes. In other words, as the current increases, the time required for opening the switch decreases. As a further advantage of my invention the device is entirely autoinatic in its action; does not require manual re-setting. The employment ot an overloadrelay, such as here shown, in connection with the time-limit device, 'for opening the switch instantly, in case the current is a heavy one, is desirable.

My invention is equally applicable to a single-phase system, and, in Fig. 5, a diagram'of such a system is illustrated, wherein the same elements are employed.

I claim:

1. In combination with an electric-circuit having an overload-current relay, of a timel-imit dev'ce for an electric-switch consisting of a circuit-controlling device for the circuit of said switch, an operating device for said circuit-controlling device requiring a prolonged interval of time for its operation, an electric-motor controlied by the overload-current relay i cr actuating said operating-device, at a variable speed according to the strength of the overload-current, means operated by the motor at a variable speed according to speed of the anotor for connecting said operating-device with the motor and means to automatically reset said operating-device to normal when said motor ceases to operate, substantially as described.

2. In combination with an electiric- :i'i.'cuit having an overload-current,relay, of a timelimit device 'for an electric-switch consisting of a circiiit-controlling device for the circuit of said switch, an operating-device for said circuit-controlling device requiring a prolonged interval of time for its operation, an

actuating-member into and out of engagement with which said operating-device is movable, an electric-motor controlled by said 'overload current relay for moving said actuating-member at a variable speed according to the strength ofthe overload-current, and means also operated by said motor at a variable speed according to the speed of the motor for controlling the engagement of said operating-device with said actuating-member, whereby said operating-device is actuated at a variable speed, and means to automatically reset said operatingdevice when the motor ceases to operate, substantially as described.

3. A time-limit device for electric-switches consisting of a circuit-controlling device for controlling the circuit of the electric-switch, an operating-device for said circuit-controlling device, an actuating-member into and out of engagement with which said operating-device is movable, means operated by the actuating-member for moving said operating-device into engagement with it, and a motor for operating said actuating-member, substantially as described.

4. A time-limit device for electric-switches consistingof a circuit-controlling device for controlling the circuit of the 'electricswitch, an operating-device for said circuit-controlling device, an actuating-member into and out of engagement with which said operating-device is movable, means operated by the actuating-member for moving said operating-device into engagement with it, means for resetting saidope'rating-device when disengaged itrom the actuating-member, and a motor for operating said actuatinganember, substantially as described.

5. 'A time-limit device for electric-switches consisting of a circuit-controlling device for controlling the circuit of the electric-switch, an operating-device for said circuit-controlling device, an actuating-member into and out of engagement with which said-operating-device is movable, an electric-motor arranged to operate said actuating-member at a variable speed, whereby the operatingdevice is correspondingly operated at a variable speed when in engagement therewith, and means operated by said motor at a variable speed according to the speed of the motor for moving said operating-device into and out of engagement with said actuatingmember, substantially as described. I

6. A time-limit device for electric-switches consisting of a circuit-controlling device for controlling the circuit of the electric-switch, an operating-device for said circuit-controlling device, an actuating member into and out of engagement withwhich said operating-device is movable, an electric-motor ar-' ranged to operate said actuating-member at .a variable speed, whereby the operating-deing said operating-device into and out of engagement with said actuating-member, substantially as described.

7. A time-limit device for electric switches consisting of a circu'it-control-ling devicefor controlling the circuit of the electric-switch, an operating-device for said circuit-controlling device, an actuating-member into and out of engagement with which said operating-device is movable, an-electric-motor arranged to operate said actuating-member at a variable speed, whereby the operating-device is correspondingly operated at a variable speed when in engagement therewith, means operated by said motor at a variable speed according to the speed of the motor for moving said operating-device into and out of engagement with said actuating member, and means for resetting said operatingdevice to normal when disengaged from the actuating-member, substantially as described.

8. A time-limit device for electric-switches consisting of a controlling-device for the electric-switch, a rotatable-member for operating it, a rotatableactuator for said member into and out of engagement with which it is movable, and mechanical means operated by an electric-motor, for moving said rotatable-member into and 'out'of engagement with said rotatable-actuator, substantially as described.

9. A time-limit device for electric-switches consisting of a controlling-device for the electric-switch, a rotatable-member for operating it, a rotatable-actuator for said member into and out of engagement with which it is movable, an electric-motor for rotating said actuator, and means, also operated by said motor, for controlling the engagement of said rotatable-member and actuator, substantially as described.

10. A time-limit device for electricswitches consisting of a controlling-device for the electric-switch, a rotatable-member for operating it, a rotatable-actuator for said member into and out of engagement with which it is movable, an electric-motor adapted to rotate said actuator at a variable speed, according to the speed of the motor, and means also operated by :said motor for controlling the engagement of said rotatable-member and actuator, substantially as described. I

11. A time-limit device for electricswitches consisting of a controlling device for the electric-switch, a rotatable-member for operating it, a rotatable actuator forv worm-wheel is movable, an electric-motor for revolving said worm at a variable speed, i and mechamcal means operated by said electric-motor for moving said worm-wheel into engagement with the'worm, substantially as described.

13. A time-limit device for electricswitches consisting of a controlling-device for the electric-switch, a worm-wheel, a worm for revolving said worm-wheel into and out of engagement with which said worm-wheel is movable, an electric-motor for revolving said worm at a variable speed, and means operated b said motor for moving said worm-wheel mto engagement with the worm, substantially as described.

let. A time-limit device for electricswitches consisting of a controllin -device for the electric-switch, a worm-whe5 having means for operating said controllin device, a. worm arranged adjacent to sai wormwheel, into and out of engagement with which said worm-wheel is movable, an electric-motor for revolving said worm at a variable speed, and means operated by said motor for moving said worm-wheel into engagement with the worm, substantially as described.

15. A time-limit device for elect-ricswitches consisting of a controlling-device for the electric-switch, a worm-wheel having means for operating it, a worm into and out of engagement with which said worm-wheel is movable, a shaft bearing said worm, a device operated by it adapted to operate by centrifugal action to move the worm-wheel into engagement with the worm, and means for revolving said shaft, substantially as described.

' 16. A time-limit device for electricswitches consisting of a controlling device for the electric-switch, a worm-wheel having means for operating it, an electric-motor having the characteristics of a series type of motor, a worm on the shaft of said motor into and out of engagement with which said worm-wheel is movable, a centrifugal act ng device arranged on said shaft for moving the worm-wheel into engagement with the worm when the shaft revolves, and a spring for resetting said worm-wheel when disengaged from the worm, substantially as described. 17. In combination with an BlGCtllCfilIICtllt having an overload-current relay, of a timelimit device for an electric-switch consisting of the circuit-controlling device for the circuit of said switch, an operating-device for said circuit controlling device requiring a prolonged interval of time for its operation, an electric-motor controlled by the overload current relayfor actuating said operatingdevice at a variable speed according to the strength of the overload-current,.means operated by said motor at a variable speed according to the speed of the motor for connecting said operating-device with the m0- tor, means to restqre said connectin means when the motor ceases tooperate an means to automatically reset said operating-device to normal'when said motor ceases to operate, substantially as described.

GEORGE A. BURNHAM.

\Vitnesses:

H. B. DAVIs, B. J. NOYES. 

